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Tectonic Summary

Seismotectonics of the Eastern Margin of the Australia Plate

The eastern margin of the Australia plate is one of the most sesimically active areas of the world due to high rates of convergence between the Australia and Pacific plates. In the region of New Zealand, the 3000 km long Australia-Pacific plate boundary extends from south of Macquarie Island to the southern Kermadec Island chain. It includes an oceanic transform (the Macquarie Ridge), two oppositely verging subduction zones (Puysegur and Hikurangi), and a transpressive continental transform, the Alpine Fault through South Island, New Zealand.

Since 1900 there have been 15 M7.5+ earthquakes recorded near New Zealand. Nine of these, and the four largest, occurred along or near the Macquarie Ridge, including the 1989 M8.2 event on the ridge itself, and the 2004 M8.1 event 200 km to the west of the plate boundary, reflecting intraplate deformation. The largest recorded earthquake in New Zealand itself was the 1931 M7.8 Hawke's Bay earthquake, which killed 256 people. The last M7.5+ earthquake along the Alpine Fault was 170 years ago; studies of the faults' strain accumulation suggest that similar events are likely to occur again.

North of New Zealand, the Australia-Pacific boundary stretches east of Tonga and Fiji to 250 km south of Samoa. For 2,200 km the trench is approximately linear, and includes two segments where old (>120 Myr) Pacific oceanic lithosphere rapidly subducts westward (Kermadec and Tonga). At the northern end of the Tonga trench, the boundary curves sharply westward and changes along a 700 km-long segment from trench-normal subduction, to oblique subduction, to a left lateral transform-like structure.

Australia-Pacific convergence rates increase northward from 60 mm/yr at the southern Kermadec trench to 90 mm/yr at the northern Tonga trench; however, significant back arc extension (or equivalently, slab rollback) causes the consumption rate of subducting Pacific lithosphere to be much faster. The spreading rate in the Havre trough, west of the Kermadec trench, increases northward from 8 to 20 mm/yr. The southern tip of this spreading center is propagating into the North Island of New Zealand, rifting it apart. In the southern Lau Basin, west of the Tonga trench, the spreading rate increases northward from 60 to 90 mm/yr, and in the northern Lau Basin, multiple spreading centers result in an extension rate as high as 160 mm/yr. The overall subduction velocity of the Pacific plate is the vector sum of Australia-Pacific velocity and back arc spreading velocity: thus it increases northward along the Kermadec trench from 70 to 100 mm/yr, and along the Tonga trench from 150 to 240 mm/yr.

The Kermadec-Tonga subduction zone generates many large earthquakes on the interface between the descending Pacific and overriding Australia plates, within the two plates themselves and, less frequently, near the outer rise of the Pacific plate east of the trench. Since 1900, 40 M7.5+ earthquakes have been recorded, mostly north of 30°S. However, it is unclear whether any of the few historic M8+ events that have occurred close to the plate boundary were underthrusting events on the plate interface, or were intraplate earthquakes. On September 29, 2009, one of the largest normal fault (outer rise) earthquakes ever recorded (M8.1) occurred south of Samoa, 40 km east of the Tonga trench, generating a tsunami that killed at least 180 people.

Across the North Fiji Basin and to the west of the Vanuatu Islands, the Australia plate again subducts eastwards beneath the Pacific, at the North New Hebrides trench. At the southern end of this trench, east of the Loyalty Islands, the plate boundary curves east into an oceanic transform-like structure analogous to the one north of Tonga.

Australia-Pacific convergence rates increase northward from 80 to 90 mm/yr along the North New Hebrides trench, but the Australia plate consumption rate is increased by extension in the back arc and in the North Fiji Basin. Back arc spreading occurs at a rate of 50 mm/yr along most of the subduction zone, except near ~15°S, where the D'Entrecasteaux ridge intersects the trench and causes localized compression of 50 mm/yr in the back arc. Therefore, the Australia plate subduction velocity ranges from 120 mm/yr at the southern end of the North New Hebrides trench, to 40 mm/yr at the D'Entrecasteaux ridge-trench intersection, to 170 mm/yr at the northern end of the trench.

Large earthquakes are common along the North New Hebrides trench and have mechanisms associated with subduction tectonics, though occasional strike slip earthquakes occur near the subduction of the D'Entrecasteaux ridge. Within the subduction zone 34 M7.5+ earthquakes have been recorded since 1900. On October 7, 2009, a large interplate thrust fault earthquake (M7.6) in the northern North New Hebrides subduction zone was followed 15 minutes later by an even larger interplate event (M7.8) 60 km to the north. It is likely that the first event triggered the second of the so-called earthquake "doublet".

This, similarly to Spaceweather, is being created as a log of events one can quickly go to a review before the event page actually goes out of scope. There's nothing wrong with discussing the events here, but if something is of world significance, such as a disaster, a separate thread is encouraged.

__________________The universe is a hairball. It was created by Fritz the Cat. :P Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.

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Tectonic Summary

Seismotectonics of the Philippine Sea and Vicinity

The Philippine Sea plate is bordered by the larger Pacific and Eurasia plates and the smaller Sunda plate. The Philippine Sea plate is unusual in that its borders are nearly all zones of plate convergence. The Pacific plate is subducted into the mantle, south of Japan, beneath the Izu-Bonin and Mariana island arcs, which extend more than 3,000 km along the eastern margin of the Philippine Sea plate. This subduction zone is characterized by rapid plate convergence and high-level seismicity extending to depths of over 600 km. In spite of this extensive zone of plate convergence, the plate interface has been associated with few great (M>8.0) ‘megathrust’ earthquakes. This low seismic energy release is thought to result from weak coupling along the plate interface (Scholz and Campos, 1995). These convergent plate margins are also associated with unusual zones of back-arc extension (along with resulting seismic activity) that decouple the volcanic island arcs from the remainder of the Philippine Sea Plate (Karig et al., 1978; Klaus et al., 1992).

South of the Mariana arc, the Pacific plate is subducted beneath the Yap Islands along the Yap trench. The long zone of Pacific plate subduction at the eastern margin of the Philippine Sea Plate is responsible for the generation of the deep Izu-Bonin, Mariana, and Yap trenches as well as parallel chains of islands and volcanoes, typical of circum-pacific island arcs. Similarly, the northwestern margin of the Philippine Sea plate is subducting beneath the Eurasia plate along a convergent zone, extending from southern Honshu to the northeastern coast of Taiwan, manifested by the Ryukyu Islands and the Nansei-Shoto (Ryukyu) trench. The Ryukyu Subduction Zone is associated with a similar zone of back-arc extension, the Okinawa Trough. At Taiwan, the plate boundary is characterized by a zone of arc-continent collision, whereby the northern end of the Luzon island arc is colliding with the buoyant crust of the Eurasia continental margin offshore China.

Along its western margin, the Philippine Sea plate is associated with a zone of oblique convergence with the Sunda Plate. This highly active convergent plate boundary extends along both sides the Philippine Islands, from Luzon in the north to the Celebes Islands in the south. The tectonic setting of the Philippines is unusual in several respects: it is characterized by opposite-facing subduction systems on its east and west sides; the archipelago is cut by a major transform fault, the Philippine Fault; and the arc complex itself is marked by active volcanism, faulting, and high seismic activity. Subduction of the Philippine Sea Plate occurs at the eastern margin of the archipelago along the Philippine Trench and its northern extension, the East Luzon Trough. The East Luzon Trough is thought to be an unusual example of a subduction zone in the process of formation, as the Philippine Trench system gradually extends northward (Hamburger et al., 1983). On the west side of Luzon, the Sunda Plate subducts eastward along a series of trenches, including the Manila Trench in the north, the smaller less well-developed Negros Trench in the central Philippines, and the Sulu and Cotabato trenches in the south (Cardwell et al., 1980). At its northern and southern terminations, subduction at the Manila Trench is interrupted by arc-continent collision, between the northern Philippine arc and the Eurasian continental margin at Taiwan and between the Sulu-Borneo Block and Luzon at the island of Mindoro. The Philippine fault, which extends over 1,200 km within the Philippine arc, is seismically active. The fault has been associated with major historical earthquakes, including the destructive M7.6 Luzon earthquake of 1990 (Yoshida and Abe, 1992). A number of other active intra-arc fault systems are associated with high seismic activity, including the Cotabato Fault and the Verde Passage-Sibuyan Sea Fault (Galgana et al., 2007).

Relative plate motion vectors near the Philippines (about 80 mm/yr) is oblique to the plate boundary along the two plate margins of central Luzon, where it is partitioned into orthogonal plate convergence along the trenches and nearly pure translational motion along the Philippine Fault (Barrier et al., 1991). Profiles B and C reveal evidence of opposing inclined seismic zones at intermediate depths (roughly 70-300 km) and complex tectonics at the surface along the Philippine Fault.

Several relevant tectonic elements, plate boundaries and active volcanoes, provide a context for the seismicity presented on the main map. The plate boundaries are most accurate along the axis of the trenches and more diffuse or speculative in the South China Sea and Lesser Sunda Islands. The active volcanic arcs (Siebert and Simkin, 2002) follow the Izu, Volcano, Mariana, and Ryukyu island chains and the main Philippine islands parallel to the Manila, Negros, Cotabato, and Philippine trenches.

Seismic activity along the boundaries of the Philippine Sea Plate (Allen et al., 2009) has produced 7 great (M>8.0) earthquakes and 250 large (M>7) events. Among the most destructive events were the 1923 Kanto, the 1948 Fukui and the 1995 Kobe (Japan) earthquakes (99,000, 5,100, and 6,400 casualties, respectively), the 1935 and the 1999 Chi-Chi (Taiwan) earthquakes (3,300 and 2,500 casualties, respectively), and the 1976 M7.6 Moro Gulf and 1990 M7.6 Luzon (Philippines) earthquakes (7,100 and 2,400 casualties, respectively). There have also been a number of tsunami-generating events in the region, including the Moro Gulf earthquake, whose tsunami resulted in more than 5000 deaths.

__________________The universe is a hairball. It was created by Fritz the Cat. :P Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.

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Tectonic Summary

Seismotectonics of South America (Nazca Plate Region)

The South American arc extends over 7,000 km, from the Chilean margin triple junction offshore of southern Chile to its intersection with the Panama fracture zone, offshore of the southern coast of Panama in Central America. It marks the plate boundary between the subducting Nazca plate and the South America plate, where the oceanic crust and lithosphere of the Nazca plate begin their descent into the mantle beneath South America. The convergence associated with this subduction process is responsible for the uplift of the Andes Mountains, and for the active volcanic chain present along much of this deformation front. Relative to a fixed South America plate, the Nazca plate moves slightly north of eastwards at a rate varying from approximately 80 mm/yr in the south to approximately 65 mm/yr in the north. Although the rate of subduction varies little along the entire arc, there are complex changes in the geologic processes along the subduction zone that dramatically influence volcanic activity, crustal deformation, earthquake generation and occurrence all along the western edge of South America.

Most of the large earthquakes in South America are constrained to shallow depths of 0 to 70 km resulting from both crustal and interplate deformation. Crustal earthquakes result from deformation and mountain building in the overriding South America plate and generate earthquakes as deep as approximately 50 km. Interplate earthquakes occur due to slip along the dipping interface between the Nazca and the South American plates. Interplate earthquakes in this region are frequent and often large, and occur between the depths of approximately 10 and 60 km. Since 1900, numerous magnitude 8 or larger earthquakes have occurred on this subduction zone interface that were followed by devastating tsunamis, including the 1960 M9.5 earthquake in southern Chile, the largest instrumentally recorded earthquake in the world. Other notable shallow tsunami-generating earthquakes include the 1906 M8.5 earthquake near Esmeraldas, Ecuador, the 1922 M8.5 earthquake near Coquimbo, Chile, the 2001 M8.4 Arequipa, Peru earthquake, the 2007 M8.0 earthquake near Pisco, Peru, and the 2010 M8.8 Maule, Chile earthquake located just north of the 1960 event.

Large intermediate-depth earthquakes (those occurring between depths of approximately 70 and 300 km) are relatively limited in size and spatial extent in South America, and occur within the Nazca plate as a result of internal deformation within the subducting plate. These earthquakes generally cluster beneath northern Chile and southwestern Bolivia, and to a lesser extent beneath northern Peru and southern Ecuador, with depths between 110 and 130 km. Most of these earthquakes occur adjacent to the bend in the coastline between Peru and Chile. The most recent large intermediate-depth earthquake in this region was the 2005 M7.8 Tarapaca, Chile earthquake.

Earthquakes can also be generated to depths greater than 600 km as a result of continued internal deformation of the subducting Nazca plate. Deep-focus earthquakes in South America are not observed from a depth range of approximately 300 to 500 km. Instead, deep earthquakes in this region occur at depths of 500 to 650 km and are concentrated into two zones: one that runs beneath the Peru-Brazil border and another that extends from central Bolivia to central Argentina. These earthquakes generally do not exhibit large magnitudes. An exception to this was the 1994 Bolivian earthquake in northwestern Bolivia. This M8.2 earthquake occurred at a depth of 631 km, making it the largest deep-focus earthquake instrumentally recorded, and was felt widely throughout South and North America.

Subduction of the Nazca plate is geometrically complex and impacts the geology and seismicity of the western edge of South America. The intermediate-depth regions of the subducting Nazca plate can be segmented into five sections based on their angle of subduction beneath the South America plate. Three segments are characterized by steeply dipping subduction; the other two by near-horizontal subduction. The Nazca plate beneath northern Ecuador, southern Peru to northern Chile, and southern Chile descend into the mantle at angles of 25° to 30°. In contrast, the slab beneath southern Ecuador to central Peru, and under central Chile, is subducting at a shallow angle of approximately 10° or less. In these regions of “flat-slab” subduction, the Nazca plate moves horizontally for several hundred kilometers before continuing its descent into the mantle, and is shadowed by an extended zone of crustal seismicity in the overlying South America plate. Although the South America plate exhibits a chain of active volcanism resulting from the subduction and partial melting of the Nazca oceanic lithosphere along most of the arc, these regions of inferred shallow subduction correlate with an absence of volcanic activity.

__________________The universe is a hairball. It was created by Fritz the Cat. :P Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.

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Tectonic Summary

Seismotectonics of the Eastern Margin of the Australia Plate

The eastern margin of the Australia plate is one of the most sesimically active areas of the world due to high rates of convergence between the Australia and Pacific plates. In the region of New Zealand, the 3000 km long Australia-Pacific plate boundary extends from south of Macquarie Island to the southern Kermadec Island chain. It includes an oceanic transform (the Macquarie Ridge), two oppositely verging subduction zones (Puysegur and Hikurangi), and a transpressive continental transform, the Alpine Fault through South Island, New Zealand.

Since 1900 there have been 15 M7.5+ earthquakes recorded near New Zealand. Nine of these, and the four largest, occurred along or near the Macquarie Ridge, including the 1989 M8.2 event on the ridge itself, and the 2004 M8.1 event 200 km to the west of the plate boundary, reflecting intraplate deformation. The largest recorded earthquake in New Zealand itself was the 1931 M7.8 Hawke's Bay earthquake, which killed 256 people. The last M7.5+ earthquake along the Alpine Fault was 170 years ago; studies of the faults' strain accumulation suggest that similar events are likely to occur again.

North of New Zealand, the Australia-Pacific boundary stretches east of Tonga and Fiji to 250 km south of Samoa. For 2,200 km the trench is approximately linear, and includes two segments where old (>120 Myr) Pacific oceanic lithosphere rapidly subducts westward (Kermadec and Tonga). At the northern end of the Tonga trench, the boundary curves sharply westward and changes along a 700 km-long segment from trench-normal subduction, to oblique subduction, to a left lateral transform-like structure.

Australia-Pacific convergence rates increase northward from 60 mm/yr at the southern Kermadec trench to 90 mm/yr at the northern Tonga trench; however, significant back arc extension (or equivalently, slab rollback) causes the consumption rate of subducting Pacific lithosphere to be much faster. The spreading rate in the Havre trough, west of the Kermadec trench, increases northward from 8 to 20 mm/yr. The southern tip of this spreading center is propagating into the North Island of New Zealand, rifting it apart. In the southern Lau Basin, west of the Tonga trench, the spreading rate increases northward from 60 to 90 mm/yr, and in the northern Lau Basin, multiple spreading centers result in an extension rate as high as 160 mm/yr. The overall subduction velocity of the Pacific plate is the vector sum of Australia-Pacific velocity and back arc spreading velocity: thus it increases northward along the Kermadec trench from 70 to 100 mm/yr, and along the Tonga trench from 150 to 240 mm/yr.

The Kermadec-Tonga subduction zone generates many large earthquakes on the interface between the descending Pacific and overriding Australia plates, within the two plates themselves and, less frequently, near the outer rise of the Pacific plate east of the trench. Since 1900, 40 M7.5+ earthquakes have been recorded, mostly north of 30°S. However, it is unclear whether any of the few historic M8+ events that have occurred close to the plate boundary were underthrusting events on the plate interface, or were intraplate earthquakes. On September 29, 2009, one of the largest normal fault (outer rise) earthquakes ever recorded (M8.1) occurred south of Samoa, 40 km east of the Tonga trench, generating a tsunami that killed at least 180 people.

Across the North Fiji Basin and to the west of the Vanuatu Islands, the Australia plate again subducts eastwards beneath the Pacific, at the North New Hebrides trench. At the southern end of this trench, east of the Loyalty Islands, the plate boundary curves east into an oceanic transform-like structure analogous to the one north of Tonga.

Australia-Pacific convergence rates increase northward from 80 to 90 mm/yr along the North New Hebrides trench, but the Australia plate consumption rate is increased by extension in the back arc and in the North Fiji Basin. Back arc spreading occurs at a rate of 50 mm/yr along most of the subduction zone, except near ~15°S, where the D'Entrecasteaux ridge intersects the trench and causes localized compression of 50 mm/yr in the back arc. Therefore, the Australia plate subduction velocity ranges from 120 mm/yr at the southern end of the North New Hebrides trench, to 40 mm/yr at the D'Entrecasteaux ridge-trench intersection, to 170 mm/yr at the northern end of the trench.

Large earthquakes are common along the North New Hebrides trench and have mechanisms associated with subduction tectonics, though occasional strike slip earthquakes occur near the subduction of the D'Entrecasteaux ridge. Within the subduction zone 34 M7.5+ earthquakes have been recorded since 1900. On October 7, 2009, a large interplate thrust fault earthquake (M7.6) in the northern North New Hebrides subduction zone was followed 15 minutes later by an even larger interplate event (M7.8) 60 km to the north. It is likely that the first event triggered the second of the so-called earthquake "doublet".

Additional Data Contributors

__________________The universe is a hairball. It was created by Fritz the Cat. :P Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.

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Tectonic Summary

The May 24, 2013 Mw 8.3 earthquake beneath the Sea of Okhotsk, Russia, occurred as a result of normal faulting at a depth of approximately 600 km. At the latitude of this earthquake, the Pacific and North America plates are converging at a rate of approximately 78 mm/yr in a west-northwest – east-southeast direction, resulting in the subduction of the Pacific plate beneath Eurasia at the Kuril-Kamchatka trench. Note that some authors divide this region into several microplates that together define the relative motions between the larger Pacific, North America and Eurasia plates; these include the Okhotsk and Amur microplates that are respectively part of North America and Eurasia. The depth and faulting mechanism of the May 24 earthquake indicate that it ruptured a fault deep within the subducting Pacific lithosphere rather than on the shallow thrust interface between the two plates.

This deep section of the Pacific slab beneath the Sea of Okhotsk has hosted several large earthquakes in the past – four above M 6 within 200 km of the May 24 event since 1988. These included a M 7.7 earthquake in July 2008, 115 km to the southwest at a depth of 630 km, and a M 7.3 event in November of the same year, 95 km to the southeast at a depth of 490 km. Because of their great depths, none are known to have caused damage. Intermediate-depth (70-300 km) and deep-focus (depth > 300 km) earthquakes are distinguished from shallow earthquakes (0-70 km) by the nature of their tectonic setting, and are in general less hazardous than their shallow counterparts, though they may be felt at great distances from their epicenters. The Pacific slab in the region of the May 24 2013 earthquake is seismically active to depths of over 650 km.

Seismotectonics of the Kuril-Kamchatka Arc

The Kuril-Kamchatka arc extends approximately 2,100 km from Hokkaido, Japan, along the Kuril Islands and the Pacific coast of the Kamchatka Peninsula to its intersection with the Aleutian arc near the Commander Islands, Russia. It marks the region where the Pacific plate subducts into the mantle beneath the Okhotsk microplate, part of the larger North America plate. This subduction is responsible for the generation of the Kuril Islands chain, active volcanoes located along the entire arc, and the deep offshore Kuril-Kamchatka trench. Relative to a fixed North America plate, the Pacific plate is moving towards the northwest at a rate that increases from 75 mm/year near the northern end of the arc to 83 mm/year in the south.

Plate motion is predominantly convergent along the Kuril-Kamchatka arc with obliquity increasing towards the southern section of the arc. The subducting Pacific plate is relatively old, particularly adjacent to Kamchatka where its age is greater than 100 Ma. Consequently, the Wadati-Benioff zone is well defined to depths of approximately 650 km. The central section of the arc is comprised of an oceanic island arc system, which differs from the continental arc systems of the northern and southern sections. Oblique convergence in the southern Kuril arc results in the partitioning of stresses into both trench-normal thrust earthquakes and trench-parallel strike-slip earthquakes, and the westward translation of the Kuril forearc. This westward migration of the Kuril forearc currently results in collision between the Kuril arc in the north and the Japan arc in the south, resulting in the deformation and uplift of the Hidaka Mountains in central Hokkaido.

The Kuril-Kamchatka arc is considered one of the most seismically active regions in the world. Deformation of the overriding North America plate generates shallow crustal earthquakes, whereas slip at the subduction zone interface between the Pacific and North America plates generates interplate earthquakes that extend from near the base of the trench to depths of 40 to 60 km. At greater depths, Kuril-Kamchatka arc earthquakes occur within the subducting Pacific plate and can reach depths of approximately 650 km.

This region has frequently experienced large (M>7) earthquakes over the past century. Since 1900, seven great earthquakes (M8.3 or larger) have also occurred along the arc, with mechanisms that include interplate thrust faulting, and intraplate faulting. Damaging tsunamis followed several of the large interplate megathrust earthquakes. These events include the February 3, 1923 M8.4 Kamchatka, the November 6,1958 M8.4 Etorofu, and the September 25, 2003 M8.3 Hokkaido earthquakes. A large M8.5 megathrust earthquake occurred on October 13, 1963 off the coast of Urup, an island along the southern Kuril arc, which generated a large tsunami in the Pacific Ocean and the Sea of Okhotsk, and caused run-up wave heights of up to 4-5 m along the Kuril arc. The largest megathrust earthquake to occur along the entire Kurile-Kamchatka arc in the 20th century was the November 4, 1952 M9.0 event. This earthquake was followed by a devastating tsunami with run-up wave heights as high as 12 m along the coast of Paramushir, a small island immediately south of Kamchatka, causing significant damage to the city of Severo-Kurilsk.

On October 4,1994, a large (M8.3) intraplate event occurred within the subducted oceanic lithosphere off the coast of Shikotan Island causing intense ground shaking, landslides, and a tsunami with run-up heights of up to 10 m on the island.

The most recent megathrust earthquake in the region was the November 15, 2006 M8.3 Kuril Island event, located in the central section of the arc. Prior to this rupture, this part of the subduction zone had been recognized as a seismic gap spanning from the northeastern end of the 1963 rupture zone to the southwestern end of the 1952 rupture. Two months after the 2006 event, a great (M8.1) normal faulting earthquake occurred on January 13, 2007 in the adjacent outer rise region of the Pacific plate. It has been suggested that the 2007 event may have been caused by the stresses generated from the 2006 earthquake.

__________________The universe is a hairball. It was created by Fritz the Cat. :P Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.

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Tectonic Summary

Seismotectonics of the Eastern Margin of the Australia Plate

The eastern margin of the Australia plate is one of the most sesimically active areas of the world due to high rates of convergence between the Australia and Pacific plates. In the region of New Zealand, the 3000 km long Australia-Pacific plate boundary extends from south of Macquarie Island to the southern Kermadec Island chain. It includes an oceanic transform (the Macquarie Ridge), two oppositely verging subduction zones (Puysegur and Hikurangi), and a transpressive continental transform, the Alpine Fault through South Island, New Zealand.

Since 1900 there have been 15 M7.5+ earthquakes recorded near New Zealand. Nine of these, and the four largest, occurred along or near the Macquarie Ridge, including the 1989 M8.2 event on the ridge itself, and the 2004 M8.1 event 200 km to the west of the plate boundary, reflecting intraplate deformation. The largest recorded earthquake in New Zealand itself was the 1931 M7.8 Hawke's Bay earthquake, which killed 256 people. The last M7.5+ earthquake along the Alpine Fault was 170 years ago; studies of the faults' strain accumulation suggest that similar events are likely to occur again.

North of New Zealand, the Australia-Pacific boundary stretches east of Tonga and Fiji to 250 km south of Samoa. For 2,200 km the trench is approximately linear, and includes two segments where old (>120 Myr) Pacific oceanic lithosphere rapidly subducts westward (Kermadec and Tonga). At the northern end of the Tonga trench, the boundary curves sharply westward and changes along a 700 km-long segment from trench-normal subduction, to oblique subduction, to a left lateral transform-like structure.

Australia-Pacific convergence rates increase northward from 60 mm/yr at the southern Kermadec trench to 90 mm/yr at the northern Tonga trench; however, significant back arc extension (or equivalently, slab rollback) causes the consumption rate of subducting Pacific lithosphere to be much faster. The spreading rate in the Havre trough, west of the Kermadec trench, increases northward from 8 to 20 mm/yr. The southern tip of this spreading center is propagating into the North Island of New Zealand, rifting it apart. In the southern Lau Basin, west of the Tonga trench, the spreading rate increases northward from 60 to 90 mm/yr, and in the northern Lau Basin, multiple spreading centers result in an extension rate as high as 160 mm/yr. The overall subduction velocity of the Pacific plate is the vector sum of Australia-Pacific velocity and back arc spreading velocity: thus it increases northward along the Kermadec trench from 70 to 100 mm/yr, and along the Tonga trench from 150 to 240 mm/yr.

The Kermadec-Tonga subduction zone generates many large earthquakes on the interface between the descending Pacific and overriding Australia plates, within the two plates themselves and, less frequently, near the outer rise of the Pacific plate east of the trench. Since 1900, 40 M7.5+ earthquakes have been recorded, mostly north of 30°S. However, it is unclear whether any of the few historic M8+ events that have occurred close to the plate boundary were underthrusting events on the plate interface, or were intraplate earthquakes. On September 29, 2009, one of the largest normal fault (outer rise) earthquakes ever recorded (M8.1) occurred south of Samoa, 40 km east of the Tonga trench, generating a tsunami that killed at least 180 people.

Across the North Fiji Basin and to the west of the Vanuatu Islands, the Australia plate again subducts eastwards beneath the Pacific, at the North New Hebrides trench. At the southern end of this trench, east of the Loyalty Islands, the plate boundary curves east into an oceanic transform-like structure analogous to the one north of Tonga.

Australia-Pacific convergence rates increase northward from 80 to 90 mm/yr along the North New Hebrides trench, but the Australia plate consumption rate is increased by extension in the back arc and in the North Fiji Basin. Back arc spreading occurs at a rate of 50 mm/yr along most of the subduction zone, except near ~15°S, where the D'Entrecasteaux ridge intersects the trench and causes localized compression of 50 mm/yr in the back arc. Therefore, the Australia plate subduction velocity ranges from 120 mm/yr at the southern end of the North New Hebrides trench, to 40 mm/yr at the D'Entrecasteaux ridge-trench intersection, to 170 mm/yr at the northern end of the trench.

Large earthquakes are common along the North New Hebrides trench and have mechanisms associated with subduction tectonics, though occasional strike slip earthquakes occur near the subduction of the D'Entrecasteaux ridge. Within the subduction zone 34 M7.5+ earthquakes have been recorded since 1900. On October 7, 2009, a large interplate thrust fault earthquake (M7.6) in the northern North New Hebrides subduction zone was followed 15 minutes later by an even larger interplate event (M7.8) 60 km to the north. It is likely that the first event triggered the second of the so-called earthquake "doublet".

__________________The universe is a hairball. It was created by Fritz the Cat. :P Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.

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Tectonic Summary

Seismotectonics of the Kuril-Kamchatka Arc

The Kuril-Kamchatka arc extends approximately 2,100 km from Hokkaido, Japan, along the Kuril Islands and the Pacific coast of the Kamchatka Peninsula to its intersection with the Aleutian arc near the Commander Islands, Russia. It marks the region where the Pacific plate subducts into the mantle beneath the Okhotsk microplate, part of the larger North America plate. This subduction is responsible for the generation of the Kuril Islands chain, active volcanoes located along the entire arc, and the deep offshore Kuril-Kamchatka trench. Relative to a fixed North America plate, the Pacific plate is moving towards the northwest at a rate that increases from 75 mm/year near the northern end of the arc to 83 mm/year in the south.

Plate motion is predominantly convergent along the Kuril-Kamchatka arc with obliquity increasing towards the southern section of the arc. The subducting Pacific plate is relatively old, particularly adjacent to Kamchatka where its age is greater than 100 Ma. Consequently, the Wadati-Benioff zone is well defined to depths of approximately 650 km. The central section of the arc is comprised of an oceanic island arc system, which differs from the continental arc systems of the northern and southern sections. Oblique convergence in the southern Kuril arc results in the partitioning of stresses into both trench-normal thrust earthquakes and trench-parallel strike-slip earthquakes, and the westward translation of the Kuril forearc. This westward migration of the Kuril forearc currently results in collision between the Kuril arc in the north and the Japan arc in the south, resulting in the deformation and uplift of the Hidaka Mountains in central Hokkaido.

The Kuril-Kamchatka arc is considered one of the most seismically active regions in the world. Deformation of the overriding North America plate generates shallow crustal earthquakes, whereas slip at the subduction zone interface between the Pacific and North America plates generates interplate earthquakes that extend from near the base of the trench to depths of 40 to 60 km. At greater depths, Kuril-Kamchatka arc earthquakes occur within the subducting Pacific plate and can reach depths of approximately 650 km.

This region has frequently experienced large (M>7) earthquakes over the past century. Since 1900, seven great earthquakes (M8.3 or larger) have also occurred along the arc, with mechanisms that include interplate thrust faulting, and intraplate faulting. Damaging tsunamis followed several of the large interplate megathrust earthquakes. These events include the February 3, 1923 M8.4 Kamchatka, the November 6,1958 M8.4 Etorofu, and the September 25, 2003 M8.3 Hokkaido earthquakes. A large M8.5 megathrust earthquake occurred on October 13, 1963 off the coast of Urup, an island along the southern Kuril arc, which generated a large tsunami in the Pacific Ocean and the Sea of Okhotsk, and caused run-up wave heights of up to 4-5 m along the Kuril arc. The largest megathrust earthquake to occur along the entire Kurile-Kamchatka arc in the 20th century was the November 4, 1952 M9.0 event. This earthquake was followed by a devastating tsunami with run-up wave heights as high as 12 m along the coast of Paramushir, a small island immediately south of Kamchatka, causing significant damage to the city of Severo-Kurilsk.

On October 4,1994, a large (M8.3) intraplate event occurred within the subducted oceanic lithosphere off the coast of Shikotan Island causing intense ground shaking, landslides, and a tsunami with run-up heights of up to 10 m on the island.

The most recent megathrust earthquake in the region was the November 15, 2006 M8.3 Kuril Island event, located in the central section of the arc. Prior to this rupture, this part of the subduction zone had been recognized as a seismic gap spanning from the northeastern end of the 1963 rupture zone to the southwestern end of the 1952 rupture. Two months after the 2006 event, a great (M8.1) normal faulting earthquake occurred on January 13, 2007 in the adjacent outer rise region of the Pacific plate. It has been suggested that the 2007 event may have been caused by the stresses generated from the 2006 earthquake.

__________________The universe is a hairball. It was created by Fritz the Cat. :P Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.

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Tectonic Summary

Seismotectonics of the Philippine Sea and Vicinity

The Philippine Sea plate is bordered by the larger Pacific and Eurasia plates and the smaller Sunda plate. The Philippine Sea plate is unusual in that its borders are nearly all zones of plate convergence. The Pacific plate is subducted into the mantle, south of Japan, beneath the Izu-Bonin and Mariana island arcs, which extend more than 3,000 km along the eastern margin of the Philippine Sea plate. This subduction zone is characterized by rapid plate convergence and high-level seismicity extending to depths of over 600 km. In spite of this extensive zone of plate convergence, the plate interface has been associated with few great (M>8.0) ‘megathrust’ earthquakes. This low seismic energy release is thought to result from weak coupling along the plate interface (Scholz and Campos, 1995). These convergent plate margins are also associated with unusual zones of back-arc extension (along with resulting seismic activity) that decouple the volcanic island arcs from the remainder of the Philippine Sea Plate (Karig et al., 1978; Klaus et al., 1992).

South of the Mariana arc, the Pacific plate is subducted beneath the Yap Islands along the Yap trench. The long zone of Pacific plate subduction at the eastern margin of the Philippine Sea Plate is responsible for the generation of the deep Izu-Bonin, Mariana, and Yap trenches as well as parallel chains of islands and volcanoes, typical of circum-pacific island arcs. Similarly, the northwestern margin of the Philippine Sea plate is subducting beneath the Eurasia plate along a convergent zone, extending from southern Honshu to the northeastern coast of Taiwan, manifested by the Ryukyu Islands and the Nansei-Shoto (Ryukyu) trench. The Ryukyu Subduction Zone is associated with a similar zone of back-arc extension, the Okinawa Trough. At Taiwan, the plate boundary is characterized by a zone of arc-continent collision, whereby the northern end of the Luzon island arc is colliding with the buoyant crust of the Eurasia continental margin offshore China.

Along its western margin, the Philippine Sea plate is associated with a zone of oblique convergence with the Sunda Plate. This highly active convergent plate boundary extends along both sides the Philippine Islands, from Luzon in the north to the Celebes Islands in the south. The tectonic setting of the Philippines is unusual in several respects: it is characterized by opposite-facing subduction systems on its east and west sides; the archipelago is cut by a major transform fault, the Philippine Fault; and the arc complex itself is marked by active volcanism, faulting, and high seismic activity. Subduction of the Philippine Sea Plate occurs at the eastern margin of the archipelago along the Philippine Trench and its northern extension, the East Luzon Trough. The East Luzon Trough is thought to be an unusual example of a subduction zone in the process of formation, as the Philippine Trench system gradually extends northward (Hamburger et al., 1983). On the west side of Luzon, the Sunda Plate subducts eastward along a series of trenches, including the Manila Trench in the north, the smaller less well-developed Negros Trench in the central Philippines, and the Sulu and Cotabato trenches in the south (Cardwell et al., 1980). At its northern and southern terminations, subduction at the Manila Trench is interrupted by arc-continent collision, between the northern Philippine arc and the Eurasian continental margin at Taiwan and between the Sulu-Borneo Block and Luzon at the island of Mindoro. The Philippine fault, which extends over 1,200 km within the Philippine arc, is seismically active. The fault has been associated with major historical earthquakes, including the destructive M7.6 Luzon earthquake of 1990 (Yoshida and Abe, 1992). A number of other active intra-arc fault systems are associated with high seismic activity, including the Cotabato Fault and the Verde Passage-Sibuyan Sea Fault (Galgana et al., 2007).

Relative plate motion vectors near the Philippines (about 80 mm/yr) is oblique to the plate boundary along the two plate margins of central Luzon, where it is partitioned into orthogonal plate convergence along the trenches and nearly pure translational motion along the Philippine Fault (Barrier et al., 1991). Profiles B and C reveal evidence of opposing inclined seismic zones at intermediate depths (roughly 70-300 km) and complex tectonics at the surface along the Philippine Fault.

Several relevant tectonic elements, plate boundaries and active volcanoes, provide a context for the seismicity presented on the main map. The plate boundaries are most accurate along the axis of the trenches and more diffuse or speculative in the South China Sea and Lesser Sunda Islands. The active volcanic arcs (Siebert and Simkin, 2002) follow the Izu, Volcano, Mariana, and Ryukyu island chains and the main Philippine islands parallel to the Manila, Negros, Cotabato, and Philippine trenches.

Seismic activity along the boundaries of the Philippine Sea Plate (Allen et al., 2009) has produced 7 great (M>8.0) earthquakes and 250 large (M>7) events. Among the most destructive events were the 1923 Kanto, the 1948 Fukui and the 1995 Kobe (Japan) earthquakes (99,000, 5,100, and 6,400 casualties, respectively), the 1935 and the 1999 Chi-Chi (Taiwan) earthquakes (3,300 and 2,500 casualties, respectively), and the 1976 M7.6 Moro Gulf and 1990 M7.6 Luzon (Philippines) earthquakes (7,100 and 2,400 casualties, respectively). There have also been a number of tsunami-generating events in the region, including the Moro Gulf earthquake, whose tsunami resulted in more than 5000 deaths.

__________________The universe is a hairball. It was created by Fritz the Cat. :P Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.

Once again to remind all, these, like Spaceweather, are logged where they are for just that purpose. This keeps a running log so people can see what is going on that might affect them. If there's a quake nearby, they can know. If there's a solar probability day, they can know. Migraine sufferers can put on their aluminum helmet those days, or in an aluminum lined room. (Sad thing is the Migraine sufferer has to live part of their life in a Faraday cage.) Good place to store electronics, too.

Quakes happen and will continue to happen. Solar days are the same.__________________The universe is a hairball. It was created by Fritz the Cat. :P Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.

Impact Estimates

Estimated Fatalities

Estimated Economic Losses

Historic Seismicity

City Exposure List

See PAGER XML link (above).

PAGER content is automatically generated, and only considers losses due to structural damage. Limitations of input data, shaking estimates, and loss models may add uncertainty. PAGER results are generally available within 30 minutes of the earthquake’s occurrence. However, information on the extent of shaking will be uncertain in the minutes and hours following an earthquake and typically improves as additional sensor data and reported intensities are acquired and incorporated into models of the earthquake’s source. Users of PAGER estimates should account for uncertainty and always seek the most current PAGER release for any earthquake.

__________________The universe is a hairball. It was created by Fritz the Cat. :P Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.

Related Links

Tectonic Summary

Seismotectonics of the Mediterranean Region and Vicinity

The Mediterranean region is seismically active due to the northward convergence (4-10 mm/yr) of the African plate with respect to the Eurasian plate along a complex plate boundary. This convergence began approximately 50 Ma and was associated with the closure of the Tethys Sea. The modern day remnant of the Tethys Sea is the Mediterranean Sea. The highest rates of seismicity in the Mediterranean region are found along the Hellenic subduction zone of southern Greece, along the North Anatolian Fault Zone of western Turkey and the Calabrian subduction zone of southern Italy. Local high rates of convergence at the Hellenic subduction zone (35mm/yr) are associated with back-arc spreading throughout Greece and western Turkey above the subducting Mediterranean oceanic crust. Crustal normal faulting throughout this region is a manifestation of extensional tectonics associated with the back-arc spreading. The region of the Marmara Sea is a transition zone between this extensional regime, to the west, and the strike-slip regime of the North Anatolian Fault Zone, to the east. The North Anatolian Fault accommodates much of the right-lateral horizontal motion (23-24 mm/yr) between the Anatolian micro-plate and Eurasian plate as the Anatolian micro-plate is being pushed westward to further accommodate closure of the Mediterranean basin caused by the collision of the African and Arabian plates in southeastern Turkey. Subduction of the Mediterranean Sea floor beneath the Tyrrhenian Sea at the Calabrian subduction zone causes a significant zone of seismicity around Sicily and southern Italy. Active volcanoes are located above intermediate depth earthquakes in the Cyclades of the Aegean Sea and in southern Italy.

In the Mediterranean region there is a written record, several centuries long, documenting pre-instrumental seismicity (pre-20th century). Earthquakes have historically caused widespread damage across central and southern Greece, Cyprus, Sicily, Crete, the Nile Delta, Northern Libya, the Atlas Mountains of North Africa and the Iberian Peninsula. The 1903 M8.2 Kythera earthquake and the 1926 M7.8 Rhodes earthquakes are the largest instrumentally recorded Mediterranean earthquakes, both of which are associated with subduction zone tectonics. Between 1939 and 1999 a series of devastating M7+ strike-slip earthquakes propagated westward along the North Anatolian Fault Zone, beginning with the 1939 M7.8 Erzincan earthquake on the eastern end of the North Anatolian Fault system. The 1999 M7.6 Izmit earthquake, located on the westward end of the fault, struck one of Turkey's most densely populated and industrialized urban areas killing, more than 17,000 people. Although seismicity rates are comparatively low along the northern margin of the African continent, large destructive earthquakes have been recorded and reported from Morocco in the western Mediterranean, to the Dead Sea in the eastern Mediterranean. The 1980 M7.3 El Asnam earthquake was one of Africa's largest and most destructive earthquakes within the 20th century.

Large earthquakes throughout the Mediterranean region have also been known to produce significant and damaging tsunamis. One of the more prominent historical earthquakes within the region is the Lisbon earthquake of November 1, 1755, whose magnitude has been estimated from non-instrumental data to be about 8.0. The 1755 Lisbon earthquake is thought to have occurred within or near the Azores-Gibraltar transform fault, which defines the boundary between the African and Eurasian plates off the west coast of Morocco and Portugal. The earthquake is notable for both a large death toll of approximately 60,000 people and for generating a tsunami that swept up the Portuguese coast inundating coastal villages and Lisbon. An earthquake of approximately M8.0 near Sicily in 1693 generated a large tsunami wave that destroyed numerous towns along Sicily's east coast. The M7.2 December 28, 1908 Messina earthquake is the deadliest documented European earthquake. The combination of severe ground shaking and a local tsunami caused an estimated 60,000 to 120,000 fatalities.

__________________The universe is a hairball. It was created by Fritz the Cat. :P Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.

Related Links

Tectonic Summary

Seismotectonics of the Caribbean Region and Vicinity

Extensive diversity and complexity of tectonic regimes characterizes the perimeter of the Caribbean plate, involving no fewer than four major plates (North America, South America, Nazca, and Cocos). Inclined zones of deep earthquakes (Wadati-Benioff zones), ocean trenches, and arcs of volcanoes clearly indicate subduction of oceanic lithosphere along the Central American and Atlantic Ocean margins of the Caribbean plate, while crustal seismicity in Guatemala, northern Venezuela, and the Cayman Ridge and Cayman Trench indicate transform fault and pull-apart basin tectonics.

Along the northern margin of the Caribbean plate, the North America plate moves westwards with respect to the Caribbean plate at a velocity of approximately 20 mm/yr. Motion is accommodated along several major transform faults that extend eastward from Isla de Roatan to Haiti, including the Swan Island Fault and the Oriente Fault. These faults represent the southern and northern boundaries of the Cayman Trench. Further east, from the Dominican Republic to the Island of Barbuda, relative motion between the North America plate and the Caribbean plate becomes increasingly complex and is partially accommodated by nearly arc-parallel subduction of the North America plate beneath the Caribbean plate. This results in the formation of the deep Puerto Rico Trench and a zone of intermediate focus earthquakes (70-300 km depth) within the subducted slab. Although the Puerto Rico subduction zone is thought to be capable of generating a megathrust earthquake, there have been no such events in the past century. The last probable interplate (thrust fault) event here occurred on May 2, 1787 and was widely felt throughout the island with documented destruction across the entire northern coast, including Arecibo and San Juan. Since 1900, the two largest earthquakes to occur in this region were the August 4, 1946 M8.0 Samana earthquake in northeastern Hispaniola and the July 29, 1943 M7.6 Mona Passage earthquake, both of which were shallow thrust fault earthquakes. A significant portion of the motion between the North America plate and the Caribbean plate in this region is accommodated by a series of left-lateral strike-slip faults that bisect the island of Hispaniola, notably the Septentrional Fault in the north and the Enriquillo-Plantain Garden Fault in the south. Activity adjacent to the Enriquillo-Plantain Garden Fault system is best documented by the devastating January 12, 2010 M7.0 Haiti strike-slip earthquake, its associated aftershocks and a comparable earthquake in 1770.

Moving east and south, the plate boundary curves around Puerto Rico and the northern Lesser Antilles where the plate motion vector of the Caribbean plate relative to the North and South America plates is less oblique, resulting in active island-arc tectonics. Here, the North and South America plates subduct towards the west beneath the Caribbean plate along the Lesser Antilles Trench at rates of approximately 20 mm/yr. As a result of this subduction, there exists both intermediate focus earthquakes within the subducted plates and a chain of active volcanoes along the island arc. Although the Lesser Antilles is considered one of the most seismically active regions in the Caribbean, few of these events have been greater than M7.0 over the past century. The island of Guadeloupe was the site of one of the largest megathrust earthquakes to occur in this region on February 8, 1843, with a suggested magnitude greater than 8.0. The largest recent intermediate-depth earthquake to occur along the Lesser Antilles arc was the November 29, 2007 M7.4 Martinique earthquake northwest of Fort-De-France.

The southern Caribbean plate boundary with the South America plate strikes east-west across Trinidad and western Venezuela at a relative rate of approximately 20 mm/yr. This boundary is characterized by major transform faults, including the Central Range Fault and the Boconó-San Sebastian-El Pilar Faults, and shallow seismicity. Since 1900, the largest earthquakes to occur in this region were the October 29, 1900 M7.7 Caracas earthquake, and the July 29, 1967 M6.5 earthquake near this same region. Further to the west, a broad zone of compressive deformation trends southwestward across western Venezuela and central Columbia. The plate boundary is not well defined across northwestern South America, but deformation transitions from being dominated by Caribbean/South America convergence in the east to Nazca/South America convergence in the west. The transition zone between subduction on the eastern and western margins of the Caribbean plate is characterized by diffuse seismicity involving low- to intermediate-magnitude (M<6.0) earthquakes of shallow to intermediate depth.

The plate boundary offshore of Colombia is also characterized by convergence, where the Nazca plate subducts beneath South America towards the east at a rate of approximately 65 mm/yr. The January 31, 1906 M8.5 earthquake occurred on the shallowly dipping megathrust interface of this plate boundary segment. Along the western coast of Central America, the Cocos plate subducts towards the east beneath the Caribbean plate at the Middle America Trench. Convergence rates vary between 72-81 mm/yr, decreasing towards the north. This subduction results in relatively high rates of seismicity and a chain of numerous active volcanoes; intermediate-focus earthquakes occur within the subducted Cocos plate to depths of nearly 300 km. Since 1900, there have been many moderately sized intermediate-depth earthquakes in this region, including the September 7, 1915 M7.4 El Salvador and the October 5, 1950 M7.8 Costa Rica events.

The boundary between the Cocos and Nazca plates is characterized by a series of north-south trending transform faults and east-west trending spreading centers. The largest and most seismically active of these transform boundaries is the Panama Fracture Zone. The Panama Fracture Zone terminates in the south at the Galapagos rift zone and in the north at the Middle America trench, where it forms part of the Cocos-Nazca-Caribbean triple junction. Earthquakes along the Panama Fracture Zone are generally shallow, low- to intermediate in magnitude (M<7.2) and are characteristically right-lateral strike-slip faulting earthquakes. Since 1900, the largest earthquake to occur along the Panama Fracture Zone was the July 26, 1962 M7.2 earthquake.

__________________The universe is a hairball. It was created by Fritz the Cat. :P Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.

Related Links

Tectonic Summary

Seismotectonics of the Mediterranean Region and Vicinity

The Mediterranean region is seismically active due to the northward convergence (4-10 mm/yr) of the African plate with respect to the Eurasian plate along a complex plate boundary. This convergence began approximately 50 Ma and was associated with the closure of the Tethys Sea. The modern day remnant of the Tethys Sea is the Mediterranean Sea. The highest rates of seismicity in the Mediterranean region are found along the Hellenic subduction zone of southern Greece, along the North Anatolian Fault Zone of western Turkey and the Calabrian subduction zone of southern Italy. Local high rates of convergence at the Hellenic subduction zone (35mm/yr) are associated with back-arc spreading throughout Greece and western Turkey above the subducting Mediterranean oceanic crust. Crustal normal faulting throughout this region is a manifestation of extensional tectonics associated with the back-arc spreading. The region of the Marmara Sea is a transition zone between this extensional regime, to the west, and the strike-slip regime of the North Anatolian Fault Zone, to the east. The North Anatolian Fault accommodates much of the right-lateral horizontal motion (23-24 mm/yr) between the Anatolian micro-plate and Eurasian plate as the Anatolian micro-plate is being pushed westward to further accommodate closure of the Mediterranean basin caused by the collision of the African and Arabian plates in southeastern Turkey. Subduction of the Mediterranean Sea floor beneath the Tyrrhenian Sea at the Calabrian subduction zone causes a significant zone of seismicity around Sicily and southern Italy. Active volcanoes are located above intermediate depth earthquakes in the Cyclades of the Aegean Sea and in southern Italy.

In the Mediterranean region there is a written record, several centuries long, documenting pre-instrumental seismicity (pre-20th century). Earthquakes have historically caused widespread damage across central and southern Greece, Cyprus, Sicily, Crete, the Nile Delta, Northern Libya, the Atlas Mountains of North Africa and the Iberian Peninsula. The 1903 M8.2 Kythera earthquake and the 1926 M7.8 Rhodes earthquakes are the largest instrumentally recorded Mediterranean earthquakes, both of which are associated with subduction zone tectonics. Between 1939 and 1999 a series of devastating M7+ strike-slip earthquakes propagated westward along the North Anatolian Fault Zone, beginning with the 1939 M7.8 Erzincan earthquake on the eastern end of the North Anatolian Fault system. The 1999 M7.6 Izmit earthquake, located on the westward end of the fault, struck one of Turkey's most densely populated and industrialized urban areas killing, more than 17,000 people. Although seismicity rates are comparatively low along the northern margin of the African continent, large destructive earthquakes have been recorded and reported from Morocco in the western Mediterranean, to the Dead Sea in the eastern Mediterranean. The 1980 M7.3 El Asnam earthquake was one of Africa's largest and most destructive earthquakes within the 20th century.

Large earthquakes throughout the Mediterranean region have also been known to produce significant and damaging tsunamis. One of the more prominent historical earthquakes within the region is the Lisbon earthquake of November 1, 1755, whose magnitude has been estimated from non-instrumental data to be about 8.0. The 1755 Lisbon earthquake is thought to have occurred within or near the Azores-Gibraltar transform fault, which defines the boundary between the African and Eurasian plates off the west coast of Morocco and Portugal. The earthquake is notable for both a large death toll of approximately 60,000 people and for generating a tsunami that swept up the Portuguese coast inundating coastal villages and Lisbon. An earthquake of approximately M8.0 near Sicily in 1693 generated a large tsunami wave that destroyed numerous towns along Sicily's east coast. The M7.2 December 28, 1908 Messina earthquake is the deadliest documented European earthquake. The combination of severe ground shaking and a local tsunami caused an estimated 60,000 to 120,000 fatalities.

Impact Estimates

Estimated Fatalities

Estimated Economic Losses

Historic Seismicity

City Exposure List

See PAGER XML link (above).

PAGER content is automatically generated, and only considers losses due to structural damage. Limitations of input data, shaking estimates, and loss models may add uncertainty. PAGER results are generally available within 30 minutes of the earthquake’s occurrence. However, information on the extent of shaking will be uncertain in the minutes and hours following an earthquake and typically improves as additional sensor data and reported intensities are acquired and incorporated into models of the earthquake’s source. Users of PAGER estimates should account for uncertainty and always seek the most current PAGER release for any earthquake.

The use of EQXML formatted data is temporary. This data will be changing to QuakeML v1.2RC3 format.

__________________The universe is a hairball. It was created by Fritz the Cat. :P Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.

Related Links

Additional Data Contributors

__________________The universe is a hairball. It was created by Fritz the Cat. :P Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.

Related Links

Tectonic Summary

Seismotectonics of the New Guinea Region and Vicinity

The Australia-Pacific plate boundary is over 4000 km long on the northern margin, from the Sunda (Java) trench in the west to the Solomon Islands in the east. The eastern section is over 2300 km long, extending west from northeast of the Australian continent and the Coral Sea until it intersects the east coast of Papua New Guinea. The boundary is dominated by the general northward subduction of the Australia plate.

Along the South Solomon trench, the Australia plate converges with the Pacific plate at a rate of approximately 95 mm/yr towards the east-northeast. Seismicity along the trench is dominantly related to subduction tectonics and large earthquakes are common: there have been 13 M7.5+ earthquakes recorded since 1900. On April 1, 2007, a M8.1 interplate megathrust earthquake occurred at the western end of the trench, generating a tsunami and killing at least 40 people. This was the third M8.1 megathrust event associated with this subduction zone in the past century; the other two occurred in 1939 and 1977.

Further east at the New Britain trench, the relative motions of several microplates surrounding the Australia-Pacific boundary, including north-south oriented seafloor spreading in the Woodlark Basin south of the Solomon Islands, maintain the general northward subduction of Australia-affiliated lithosphere beneath Pacific-affiliated lithosphere. Most of the large and great earthquakes east of New Guinea are related to this subduction; such earthquakes are particularly concentrated at the cusp of the trench south of New Ireland. 33 M7.5+ earthquakes have been recorded since 1900, including three shallow thrust fault M8.1 events in 1906, 1919, and 2007.

The western end of the Australia-Pacific plate boundary is perhaps the most complex portion of this boundary, extending 2000 km from Indonesia and the Banda Sea to eastern New Guinea. The boundary is dominantly convergent along an arc-continent collision segment spanning the width of New Guinea, but the regions near the edges of the impinging Australia continental margin also include relatively short segments of extensional, strike-slip and convergent deformation. The dominant convergence is accommodated by shortening and uplift across a 250-350 km-wide band of northern New Guinea, as well as by slow southward-verging subduction of the Pacific plate north of New Guinea at the New Guinea trench. Here, the Australia-Pacific plate relative velocity is approximately 110 mm/yr towards the northeast, leading to the 2-8 mm/yr uplift of the New Guinea Highlands.

Whereas the northern band of deformation is relatively diffuse east of the Indonesia-Papua New Guinea border, in western New Guinea there are at least two small (<100,000 km²) blocks of relatively undeformed lithosphere. The westernmost of these is the Birds Head Peninsula microplate in Indonesia's West Papua province, bounded on the south by the Seram trench. The Seram trench was originally interpreted as an extreme bend in the Sunda subduction zone, but is now thought to represent a southward-verging subduction zone between Birds Head and the Banda Sea.

There have been 22 M7.5+ earthquakes recorded in the New Guinea region since 1900. The dominant earthquake mechanisms are thrust and strike slip, associated with the arc-continent collision and the relative motions between numerous local microplates. The largest earthquake in the region was a M8.2 shallow thrust fault event in the northern Papua province of Indonesia that killed 166 people in 1996.

The western portion of the northern Australia plate boundary extends approximately 4800 km from New Guinea to Sumatra and primarily separates Australia from the Eurasia plate, including the Sunda block. This portion is dominantly convergent and includes subduction at the Sunda (Java) trench, and a young arc-continent collision.

In the east, this boundary extends from the Kai Islands to Sumba along the Timor trough, offset from the Sunda trench by 250 km south of Sumba. Contrary to earlier tectonic models in which this trough was interpreted as a subduction feature continuous with the Sunda subduction zone, it is now thought to represent a subsiding deformational feature related to the collision of the Australia plate continental margin and the volcanic arc of the Eurasia plate, initiating in the last 5-8 Myr. Before collision began, the Sunda subduction zone extended eastward to at least the Kai Islands, evidenced by the presence of a northward-dipping zone of seismicity beneath Timor Leste. A more detailed examination of the seismic zone along it's eastern segment reveals a gap in intermediate depth seismicity under Timor and seismic mechanisms that indicate an eastward propagating tear in the descending slab as the negatively buoyant oceanic lithosphere detaches from positively buoyant continental lithosphere. On the surface, GPS measurements indicate that the region around Timor is currently no longer connected to the Eurasia plate, but instead is moving at nearly the same velocity as the Australia plate, another consequence of collision.

Large earthquakes in eastern Indonesia occur frequently but interplate megathrust events related to subduction are rare; this is likely due to the disconnection of the descending oceanic slab from the continental margin. There have been 9 M7.5+ earthquakes recorded from the Kai Islands to Sumba since 1900. The largest was the great Banda Sea earthquake of 1938 (M8.5) an intermediate depth thrust faulting event that did not cause significant loss of life.

Impact Estimates

Estimated Fatalities

Estimated Economic Losses

Historic Seismicity

City Exposure List

See PAGER XML link (above).

PAGER content is automatically generated, and only considers losses due to structural damage. Limitations of input data, shaking estimates, and loss models may add uncertainty. PAGER results are generally available within 30 minutes of the earthquake’s occurrence. However, information on the extent of shaking will be uncertain in the minutes and hours following an earthquake and typically improves as additional sensor data and reported intensities are acquired and incorporated into models of the earthquake’s source. Users of PAGER estimates should account for uncertainty and always seek the most current PAGER release for any earthquake.

Data Contributors

__________________The universe is a hairball. It was created by Fritz the Cat. :P Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.

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